Pyrrole carbonitrile and nitropyrrole compounds are disclosed to be useful as insecticidal, acaricidal and molluscicidal agents in U.S. Pat. Nos. 5,162,308 and 5,204,332. Those patents also refer to 2,4,5-tribromopyrrole-3-carbonitrile, its molluscicidal use and its preparation via bromination of pyrrole-3-carbonitrile. However, pyrrole-3-carbonitrile and its derivatives are difficult to prepare. Literature methods, such as that reported by A. M. van Leusen, et al., Tetrahedron Letters, 5337, (1972), report yields of 10% or less.
The preparation of 2,4,5-tribromopyrrole-3-carbonitrile from 2-trihaloacetylpyrrole-4-carbonitrile compounds is described in United States Patent 5,008,403. However, that process is not well suited for use in large scale preparations of 2,4,5-tribromopyrrole-3-carbonitrile.
It is therefore an object of the present invention to provide a new and efficient process for preparing 2,4,5-tribromopyrrole-3-carbonitrile.